Needlestick prevention device

ABSTRACT

A needlestick prevention device for an injection device ( 1 ) having a hollow needle ( 2 ) comprises a sheath having a first member ( 9 ) for attachment to the injection device ( 1 ) and a second member ( 10 ) slidable longitudinally relative to the first member ( 9 ) to expose or to cover the needle ( 2 ), and spring means ( 11 ) biasing the second member ( 10 ) to cover the needle ( 2 ). The first and second members ( 9, 10 ) have interengaging guide means ( 13 ) and locking means ( 14 ), including a first guide part ( 23 ) operative to allow free longitudinal sliding movement of the second member ( 10 ) relative to the first member ( 9 ), and a second guide part ( 24 ) operative on movement by manual relative rotation of the first and second members ( 9, 10 ) and following release of a force urging the second member ( 10 ) to expose the needle ( 2 ). The spring means ( 11 ) urges the second member ( 10 ) to cover the needle ( 2 ) and to operate the locking means ( 14 ) to retain the second member ( 10 ) covering the needle ( 2 ). This allows free movement of the second member ( 10 ) in the first guide part ( 23 ), allowing for filling of the syringe ( 1 ), but then automatic sheathing and locking when the user simply twists the second member ( 10 ) relative to the first ( 9 ).

This invention relates to a needlestick prevention device for use withinjection devices, such as syringes.

A needlestick injury generally occurs in a medical environment, andparticularly before or after use of a syringe or other injection device,when the user accidentally sticks the needle into himself or herself, orindeed another person. It is of course important to prevent suchinjuries, since they can spread infections and diseases, as well asbeing painful and possibly incapacitating.

There are several known ways of trying to prevent needlestick. Forexample, some syringes are made with needles which are retractedautomatically after use by means of a spring in the syringe. However,this requires a complex construction, and is expensive to manufacture.Further, it does not address the possibility of injury occurring beforethe injection is given.

Another known way is to replace the tubular sheath which is suppliedwith the syringe, protecting the needle. It is not now recommendedpractice to replace the sheath after the syringe has been used, becauseof the difficulty of placing the end of the needle accurately in thesheath. It is thought that trying to re-sheath the needle has actuallybeen the cause of a significant number of needlestick injuries. Further,the sheath can easily be removed again, so that injury is possible.

Yet another known needlestick prevention device is an automatic needlesheath mounted on the syringe barrel, the sheath being able to slide outto cover the needle. EP-A-0 268 445 shows a construction with astationary sheath part, and a movable sheath part spring-biassed to anextended position in which it covers the needle. The movable sheath partretracts to expose the needle for use, and when the retracting pressureis released the spring moves it automatically into its extendedposition, where it is locked. The movable sheath part has a projectionreceived in a track in the stationary part to determine its movement andto lock it. However in one embodiment the track is such that the movablesheath part can be unlocked by twisting it relative to the stationarypart, and in another its movement is dictated by the track, so that theuser has no choice about its use.

According to the present invention, a needlestick prevention device foran injection device having a hollow needle comprises a sheath having afirst member for attachment to the injection device and a second memberslidable longitudinally relative to the first member to expose or tocover the needle, and spring means biassing the second member to coverthe needle, the first and second members having interengaging guidemeans and locking means, including a first guide part operative to allowfree longitudinal sliding movement of the second member relative to thefirst member, and a second guide part operative on movement by manualrelative rotation of the first and second members and following releaseof a force urging the second member to expose the needle, in which thespring means urges the second member to cover the needle and to operatethe locking means to retain the second member covering the needle.

Thus, the invention allows free movement of the second member in thefirst guide part, allowing for filling of the syringe, expulsion of airand finding of an injection site (or a site for taking a blood sample),but then automatic sheathing and locking in the second guide part,provided by the spring means. The user simply has to twist the secondmember relative to the first to cause the automatic sheathing andlocking to operate. This provides the necessary element of choice forthe user as to when to sheath and lock the needle, while being safe touse, as the simple twisting movement carries no danger of needlestick.Indeed, the twisting can be carried out when the needle has beeninserted into the patient. The device of the invention is thereforesimple to use and to manufacture, as it has only three components.

The guide means preferably comprises at least one groove means on one ofthe first and second members, and a corresponding projection on theother of the members which slides in the groove means. Preferably twogroove means and projections are provided, arranged in diametralopposition. Conveniently the second member slides inside the firstmember. The or each groove means is then provided on the radiallyexterior surface of the second member and the or each projection on theradially interior surface of the first member. This arrangementsimplifies manufacture. It would of course be possible for the groovemeans to be on the first member and the projection on the second member.

In the or each guide means the first guide part preferably comprises afirst groove extending longitudinally of the second member. The secondguide part comprises a second groove extending longitudinally of thesecond member. The second groove is preferably parallel to the first,and spaced from it such that a relative rotation of 30° of the memberswill move the projection from the first groove into the second groove.The locking means conveniently comprises a permanent locking recessformed as part of the second groove, in which the projection isreceived. The arrangement of the permanent locking recess and projectionis such that the projection cannot be removed from the recess without aconsiderable effort on the part of the user. It cannot be removed simplyby relative rotation of the first and second members, or by applyinglongitudinal force to the second member. This ensures the safe coveringof the needle when it is desired, with the second member in a permanentlocking position.

The first groove may be provided with a temporary locking recess inwhich the projection is received. When the projection is engaged in thetemporary locking recess the needle is covered by the second member.This temporary locking position can be used when transporting filledsyringes, to prevent accidents. In order to engage the temporary lockingposition the user moves the first and second members away from eachother in the longitudinal direction. The reverse movement is applied bythe user to disengage the temporary locking position. In the temporarylocking position the second member may be slightly less extended fromthe first member than in the permanent locking position.

The or each groove means may have a further longitudinal groove with aninitial locking recess. Relative rotation of the first and secondmembers moves the projection from the further groove into the firstgroove. The further groove is used for assembly of the first and secondmembers. The spring means urges the second member to cover the needle,and so that the projection is received in the initial locking recess.This locks the second member in an initial locking position, and can beused for transit of the syringe prior to use. There is no need for aseparate needle sheath. Rotation of the second member by the user movesit out of the initial locking position and into the first groove, to beready for use.

The grooves and the projections are so shaped as to allow relativerotation of the first and second members in only one direction. Thisadds to the safety of the device. The grooves preferably have one radialwall and one curved wall, with the projections being of complementaryshape. The projections can therefore move out of a groove over thecurved wall, but cannot move back, because of the engagement of theradial walls.

The spring means preferably comprises a compression spring actingbetween the inner end of the second member and an abutment on the firstmember. The spring may also provide an additional locking mechanism whenthe second member is in its permanent locking position. The additionallocking mechanism conveniently comprises an oversize turn of the spring,adapted to be received in a radial groove in the first member when thesecond member is in its permanent locking position. This physicallyprevents re-compression of the spring, but the oversize turn does notaffect sliding movement of the two members prior to this. The spring mayalso be arranged so that the oversize turn tends to enlarge on relativerotation of the two members.

The first member may be attached to the syringe in any suitable way, forexample by a luer slip or luer lock connection to a hub at the forwardend of the syringe barrel.

An embodiment of the invention is illustrated by way of example in theaccompanying drawings, in which:

FIG. 1 is a longitudinal section through a syringe with the needlestickprevention device according to the invention;

FIG. 2 is similar to FIG. 1 but shows the needlestick prevention devicein a different position;

FIG. 3 is a cross-section on the line 3-3 of FIG. 1; and

FIG. 4 is a developed plan view of the exterior surface of part of thedevice of FIG. 1.

FIGS. 1 and 2 show a syringe 1 with a hollow needle 2 for injecting orremoving fluid from a human or animal body, and a needlestick preventiondevice 3. The needlestick prevention device allows exposure of theneedle 2 for use, and covers the needle 2 after use.

The syringe 1 is of a known type, comprising a plunger 4 with a seal 5manually reciprocable in a cylindrical barrel 6. At its distal end thebarrel 6 has a hub 7 to which the needle 2 is attached in any suitableway, while the other, proximal, end is open to allow reciprocation ofthe plunger 4. Movement of the plunger 4 in the barrel 6 expels or drawsin fluid through the needle 2.

The needlestick prevention device 3 comprises a sheath 8 surrounding theneedle 2. The sheath 8 has first and second relatively movabletelescoping tubular members 9, 10 biassed apart by a spring 11. Thefirst and second members 9, 10 are injection moulded from a plasticssuch as ABS or polycarbonate. The first outer member 9 is of greaterdiameter, and is arranged at its proximal end 12 for connection to thehub 7 of the syringe 1 in any suitable way, such as a luer slip or luerlock connection. The first outer member 9 is therefore held stationaryrelative to the barrel 6. The second inner member 10 is of lesserdiameter, and is adapted to slide longitudinally within the first member9, between an extended position shown in FIG. 1 in which it covers theneedle 2, and a retracted position shown in FIG. 2, in which the needle2 is exposed for use. The spring 11 biasses the second member 10 towardsthe extended position. The first and the second members 9, 10 are alsorelatively rotatable. Further, the first and second members 9, 10 haveinterengaging guide means 13 and locking means 14 determining movementof the second member 10.

The guide means 13 comprises groove means 15 formed in the radiallyouter surface of the inner member 10, and corresponding projections 16formed on the radially inner surface of the outer member 9. As can beseen in FIG. 3, there are two diametrally opposed groove means 15 andcorresponding projections 16.

Each projection 16 is formed as a radially inwardly projecting button 17on a radially resilient arm 18. Each arm 18 is formed between two slots19 in the distal end 20 of the first member 9. Each button 17 is shapedwith a radial wall 21 and a curved wall 22, which corresponds to theshape of the groove means 15.

One groove means 15 is shown in developed form in FIG. 4, from which itcan be seen that there are essentially three guide grooves 23, 24, 25extending longitudinally of the second member from a position adjacentits proximal end 26. The grooves 23, 24, 25 each have a radial wall 27and a curved wall 28 corresponding to the shape of the buttons 17.

The first guide groove 23 extends longitudinally for about half of thelength of the second member 10, being defined by stops 29 at each end.At its proximal end the first groove 23 has a temporary locking recess30. The button 17 can be engaged in and disengaged from the recess 30 onapplication of a manual force to the second member 10 in the appropriatedirection, but a stop 31 prevents the engagement under the force of thespring 11. The button 17 is movable in both directions in the firstguide groove 23. A wall 32 separates the first guide groove 23 from thesecond guide groove 24. The wall 32 has a lesser height at the distalend of the guide groove 23 to allow the button 17 to move into thesecond guide groove 24 on rotation of the second member 10 relative tothe first member 9.

The second guide groove 24 extends parallel to the first guide groove23. Their distal ends are aligned, but the proximal end of the secondguide groove 24 is closer to the proximal end 26 of the second member10, and has a permanent locking recess 33. The locking recess 33 is soshaped to allow the button 17 to engage in it, but to prevent itswithdrawal, by means of a stop 34. The button 17 can be engaged in therecess 33 under the force of the spring 11. It will be appreciated thatwhen the button 17 is in either the temporary locking recess 30 or thepermanent locking recess 33, the second member 10 will be in an extendedposition covering the needle 2, but in the permanent recess 33 a greateramount of the second member 10 will project beyond the end of the needle2.

The button 17 engages in the first guide groove 23 as a result ofrotation of the second member 10 relative to the first member 9, whichmoves the button 17 from the third groove 25 along an inclinedconnecting groove 35 to an intermediate position in the first groove 23on the distal side of the temporary locking recess 30. The third groove25 extends from the distal end 36 of the second member 10 to a stop 37aligned with the proximal stop 29 of the first guide groove 23. Thethird groove 25 allows for assembly of the two members 9, 10, and at itsproximal end has an initial locking recess 38, in which the button 17 isreceived at the end of the assembly process, so that the second member10 is then in the extended position. The recess 38 is formed with anabutment 39 which prevents movement of the button 17 back along thegroove 25, but allows movement into the connecting groove 35 on relativerotation of then members 9, 10. The distal end 36 of the outer member 10is formed with a curved annular flange 47 acting as a guide for the tipof the needle 2.

The spring 11 comprises a compression spring, whose distal end 40 abutsa collar 41 on the proximal end 42 of the second member 10, and whoseproximal end 43 engages an abutment 44 on the proximal end 12 of thefirst member 9. The spring 11 also has an oversize turn 45 adjacent toits distal end 40. This turn is normally in engagement with the innersurface of the first member 9, but when the second member 10 reaches thepermanent locking position with the button 17 in the recess 33, theoversize turn moves distally, and into a radial groove 46 in the firstmember 9 to provide an additional locking mechanism.

In use, the first and second members 9, 10 are assembled by sliding thesecond into the first from its proximal end 12. The spring 11 is theninserted, so that the second member 10 assumes its extended position,with the buttons 17 in the initial locking recesses 38. The secondmember 10 will be held in this position until it is rotated manuallyrelative to the first member 9 through about 30°. The device 3 can thenbe attached to a syringe 1, and will cover the needle 2 by say 1 mm sothat no further separate needle sheath is required for transit.

When the syringe 1 is to be used, the user rotates the second member 10which brings the buttons 17 into the intermediate position in the firstguide grooves 23. In this position the end of the needle 2 is uncovered,and the second member 10 can be manually retracted against the force inthe spring 11 to allow for filling of the syringe 1 and expulsion ofair, as well as the finding of an injection site and insertion of theneedle 2. The buttons 17 are freely movable in the first guide grooves23, so that the second member 10 can move between the retracted andintermediate positions as required by the user. If the syringe 1 is tobe filled at a location remote from the patient, the user can apply aforce (usually by pulling the second member 10) to engage the buttons 17in the temporary locking recesses 30. In this temporary locking positionthe needle 2 is covered again by say 1 mm, so that the syringe 1 can besafely transported. To prepare the syringe 1 for injection, the secondmember 10 is pushed towards the first member 9 to release the temporarylocking, so that the second member 10 again assumes the intermediateposition with the needle 2 exposed.

The injection can then be performed, and the user twists the secondmember 10 again to move the buttons 17 into the second grooves 24. Thispreferably occurs while the needle 2 is in the patient, either before orafter injection, as the user desires. On removal of the needle from thepatient the force urging the second member 10 into a retracted positionis released, so that the spring 11 operates to urge the second member 10away from the first member 9, causing the buttons 17 to engageautomatically in the permanent locking recesses 33. In this permanentlocking position the needle 2 is covered by say 3 mm. In the permanentlocking position the second member 10 cannot be moved towards the firstmember 9 simply by the application of a manual force. The oversize turn45 will enter the radial groove 46, to prevent relative longitudinalmovement of the members 9, 10 to provide an additional lockingmechanism. The shape of the grooves and buttons allows the buttons tomove as described above, but does not allow the reverse movement. In thecase where a sample is being taken from a patient, the temporary lockingposition may be used after the sample has been taken, if it is necessaryto transfer the sample from the syringe to another container using theneedle. The permanent locking position will be used after transfer ofthe sample.

The flange 47 acts as a trap for any fluid remaining on the needle 2after injection or the taking or transfer of a sample, if the syringe 1is put into a position where the needle 2 is pointing down. The flange47 may also act as a guard for the needle 2 in the permanent lockingposition. If the needle 2 is mounted at a slight angle, up to 5°, to thelongitudinal axis of the second member 10, it will be held straight aslong as it is in contact with the flange 47. The length of the flange 47will be chosen so that, in the permanent locking position, the needletip comes out of engagement with the flange 47. The needle 2 will thenassume an angled position, and will be caught behind the flange 47,preventing it from being exposed again.

Thus, the needlestick prevention device 3 is simple to make andassemble, and provides three different locking positions in which theneedle 2 is covered. The initial position allows for transit of theempty syringe, and obviates the need for a separate needle sheath. Thetemporary locking position allows for transport of a filled syringe(whether prior to injection or after taking of a sample), and thepermanent locking position provides for safe covering of the needle 2after final use of the syringe 1. The major advantage of the inventionis that the user chooses the point at which the permanent lockingoccurs, and that once this choice has been made the locking happensautomatically.

It will be appreciated that in a modification (not shown) the groovemeans could be on the first member 9 and the projections 16 on thesecond member 10.

Further, although the invention has been described in relation to asyringe, it can be used with other injection devices, catheters and thelike.

1. A needlestick prevention device for an injection device having ahollow needle, comprising: a sheath having a first member for attachmentto the injection device and a second member slidable longitudinallyrelative to the first member to expose or to cover the needle, andspring means biasing the second member to cover the needle, the firstand second members having interengaging guide means and locking means,characterised in that the guide means include a first guide partoperative to allow free longitudinal sliding movement of the secondmember relative to the first member, and a second guide part operativeon movement by manual relative rotation of the first and second membersand following release of a force urging the second member to expose theneedle, in which the spring means urges the second member to cover theneedle and to operate the locking means to retain the second membercovering the needle.
 2. A needlestick prevention device according toclaim 1, in which the guide means comprises at least one groove means onone of the first and second members, and a corresponding projection onthe other of the members which slides in the groove means.
 3. Aneedlestick prevention device according to claim 2, in which two groovemeans and projections are provided, arranged in diametral opposition. 4.A needlestick prevention device according to claim 1, in which thesecond member slides inside the first member.
 5. A needlestickprevention device according to claim 2, in which the or each groovemeans is provided on the radially exterior surface of the second memberand each projections on the radially interior surface of the firstmember.
 6. A needlestick prevention device according to claim 1, inwhich in the or each guide means the first guide part comprises a firstgroove extending longitudinally of the second member.
 7. A needlestickprevention device according to claim 1, in which the second guide partcomprises a second groove extending longitudinally of the second member.8. A needlestick prevention device according to claim 7, in which thesecond groove is parallel to the first, and spaced from it such that arelative rotation of 30° of the members will move the projection fromthe first groove into the second groove.
 9. A needlestick preventiondevice according to claim 8, in which the locking means comprises apermanent locking recess formed as part of the second groove, in whichthe projection is received.
 10. A needlestick prevention deviceaccording claim 9, in which the first groove is provided with atemporary locking recess in which the projection is received.
 11. Aneedlestick prevention device according to claim 10, in which in thetemporary locking position the second member is slightly less extendedfrom the first member than in the permanent locking position.
 12. Aneedlestick prevention device according to claim 2, in which the or eachgroove means has a further longitudinal groove with an initial lockingrecess.
 13. A needlestick prevention device according to claim 2, inwhich the grooves and projections are so shaped as to allow relativerotation of the first and second members in only one direction.
 14. Aneedlestick prevention device according to claim 13, in which thegrooves have one radial wall and one curved wall, with the projectionsbeing of complementary shape.
 15. A needlestick prevention deviceaccording to claim 1, in which the spring means comprises a compressionspring acting between the inner end of the second member and an abutmenton the first member.
 16. A needlestick prevention device according toclaim 15, in which the spring also provides an additional lockingmechanism when the second member is in its permanent locking position.17. A needlestick prevention device according to claim 16, in which theadditional locking mechanism comprises an oversize turn of the spring,adapted to be received in a radial groove in the first member when thesecond member is in its permanent locking position.
 18. A needlestickprevention device according to claim 17, in which the spring is alsoarranged so that the oversize turn tends to enlarge on relative rotationof the two members.
 19. A needlestick prevention device according toclaim 1, in which the injection device is a syringe additionallycomprising a barrel.
 20. A needlestick prevention device according toclaim 19, in which the first member is attached to the syringe by a luerslip connection to a hub at the forward end of the syringe barrel.
 21. Aneedlestick prevention device according to claim 19, in which the firstmember is attached to the syringe by a luer lock connection to a hub atthe forward end of the syringe barrel.